1. The Reference line, connecting the centres of area of the projected skull outline, the cranium and the face, is relatively easy to locate and forms a more stable base from which to measure changes in the face in profile including the dental base relationship, than are the sella-nasion, maxillary or mandibular planes. 2. The Reference-Profile angle is a reliable assessor of a bimaxillary prognathism or retrognathism. Its mean value is 44 degrees. Angles above this value are associated with a bimaxillary retrognathism, and angles below this value with a bimaxillary prognathism. 3. The Reference-Dental Base angle is the most consistent for assessing the anterior jaw relationship between the maxilla and mandible. Its mean value of 50 degrees indicates a Class I relationship. Angles of 53 degrees and above indicate clinical Class II cases and angles of 48 degrees and below indicate clinical Class III cases. 4. These two angles are potentially valuable diagnostic indices for use in orthodontic clinical assessment.